Apparatus for reproducing information from photon-emissive storage mediums



June 27, 1967 R w DUWE 3,328,775

APPARATUS FOR REROD UO NG INFORMATION FROM PHOTON-EMISSIVE STORAGEMEDIUMS Filed March 18, 1964 2 Sheets-Sheet 1 I NVENTOR. P055197 144fll/WE Y June 27, 1967 Filed March 18, 1964 R. W. DUWE APPARATUS FORREPRODUCING INFORMATION FROM PHOTON-EMISSIVE STORAGE MEDIUMS 2Sheets-Sheet 2 INVENTOR.

Ra's/597 Mam/E BY j 1 147 f ORA E Y5 United States Patent 3,328,775APPARATUS FOR REPRODUCING INFORMATION FROM PHOTON-EMISSIVE STORAGEMEDIUMS Robert W. Duwe, Minneapolis, Minn, assignor to Minnesota Miningand Manufacturing Company, St. Paul,

Minn, a corporation of Delaware Filed Mar. 18, 1964, Ser. No. 352,370 4Claims. (Cl. 340-173) This invention relates to a new and very usefulapparatus for readout of information from photon-emissive, electronbeam-sensitive recording media.

In one aspect, this invention relates to apparatus for serial readout ofa recording medium having a differentially photon-emissive, electronbeam-sensitive surface, the differential photon emission from suchsurface being representative of prerecorded input information.

While those sldlled in the art have long understood that excitedelectrons cause photon emission from certain types of fluorescentmaterials, so far as is known to me no one has heretofore provided meansfor collecting a maximum amount of light emitted by a differentiallyfluorescent surface when struck by an electron beam of essentiallyconstant intensity. By the present invention, a photon reflectorpositioned over a differentially photon emitting electron excitedsurface enables one to collect and reflect photon emission towards anappropriate photoelectric detection means so as to achieve superiorreadout of prerecorded information.

It is accordingly an object of the present invention to provideapparatus whereby a maximum amount of light emitted by aphoton-emissive, electron beam-sensitive surface can be collected andused for readout of information.

Another object of this invention is to provide apparatus for serialreadout of stored information from an electron beam-sensitive, photonemissive, sheet-like storage medium whereby such a medium is excitableby electrons to emit photons and such photon emission is collectable toa maximum possible extent and reflected (directed) towards photonsensitive detection means capable of continuously sensing the reflectedphoton emission.

A further object of this invention is to provide a combination of anelectron beam producing means, a photon reflective means, and a photonsensitive detection means whereby serial readout of information from adifferentially photon-emissive, electron beam-sensitive recording mediumcan be accomplished.

Other and further objects of this invention will become apparent tothose skilled in the art from a reading of the attached specification,taken together with drawings, wherein:

FIGURE 1 is a diagrammatic sectional view of one embodiment of apparatusof this invention;

FIGURE 2 is an enlarged detailed sectional view of the region beyond thebeam focusing coil rotated with respect to FIGURE 1;

FIGURE 3 is a front view of the photon reflector used in the embodimentof FIGURE 1 taken along the line 33 of FIGURE 2;

FIGURE 4 is a view similar to FIGURE 2 but showing an alternativeembodiment for an apparatus of this invention;

FIGURE 5 is a view similar to FIGURE 2, but showing another alternativeembodiment for apparatus of this invention;

FIGURE 6 is a view similar to FIGURE 2, but showing a furtheralternative embodiment;

FIGURE 7 is a partially diagrammatic view illustrating a vertical,sectional view of an alternative photon reflector construction usable inthe apparatus of this invention;

FIGURE 8 is front view of the photon reflector construction of FIGURE 7taken along the line 8-8 of FIGURE 7;

FIGURE 9 illustrates a vertical, sectional view of a further alternativeconstruction for a photon reflector usable in the apparatus of thisinvention; and

FIGURE 10 is a front view of the reflector construction of FIGURE 9.

Background technology Because those skilled in the art may not befamiliar with the technology involved, a brief description of the priorart for purposes of this invention is now given:

A storage medium useful in the apparatus of this invention is sheet-likeand initially has both:

(a) The capacity to alter selectively, chemically and internally itsinitial composition adjacent a surface thereof in response to exposureof that surface to differential irradiation, so that, either directly oras a result of subquent processing (i.e. chemical and/or physicaltreatment) of such medium, such medium thereafter differentiallyradiates (i.e., transmits, absorbs, and/or emits) photon energy in amanner representative of the initial pattern of differentialirradiation, and

(b) The capacity to emitphotons uniformly from a surface thereof inresponse to uniform electron excitation of a surface thereof.

A species example of a recording medium is as follows:

A two mil wet coating of the following homogeneous formulation is coatedonto a 0.75 mil aluminum foil substrate and then dried:

2.0 gram zinc oxide (fluorescent material) 2.0 gram copolymer of 87 molper-cent vinyl chloride and 13 mol percent vinyl acetate, 8.0 gramsacetone (opacifiable material) Using the resulting recording medium,recording is effected thereon in each of the following ways:

(a) A sample is scanned in a raster pattern under high vacuum with anintensity modulated electron beam of 20 kilovolts, 5 microampere peaktarget current in a 0.5 1O inch beam spot which scans out a 0.5 x 0.5inch raster for times ranging from to 3 seconds.

(b) A sample is flooded with a non-scanning beam through an image-wisemask of total dimensions 0.5 x 0.5 inch with a 20 kilovolt, 5microarnpere unmodulted electron beam for times ranging from to 3seconds.

(c) A sample is exposed for 5 seconds to ultraviolet light by placing it10 inches from an ultraviolet lamp, having the trade designation B-H6 assold by the General Electric Company. Thereafter, each sample is heatedto C. until a black color is formed selectively in the irradiated area.i

In each case the recorded information is retrievable by placing suchsample in a vacuum chamber and scanning same with a focused beam ofelectrons to provide an image-wise differential photon emission from thesample surface. The photon emission is caused by fluorescence of thezinc oxide in the unexposed areas (the exposed areas being effectivelymasked). Simultaneously variations in the intensity of photon emissionare detected with a photomultiplier. Owing to the fact that the photonemission from each sample in the foregoing illustration is emittedwithin a solid angle equal to the angle defined (i.e. subtended) by themedia surface at the beam impact while the total angle occupied by thephoton multiplier is but a small fraction of such solid angle, thephoton emission collection efficiency of the photomultiplier is veryinefficient. In the case where the recording medium being read out isplanar with respect to the readout beam, the photon emission takes placewithin a solid angle apoaching 27r steradians. If the recording mediumis conxly curved towards the readout beam, the photon emis- 311 isemitted over a solid angle greater than about 271' :radians. If therecording medium is concavely curved ith respect to the readout beam,then the photon emission kes place of a total solid angle less thanabout 271' eradians. It is by the apparatus of the present invention atone achieves a very useful and very eflicient retieval informationstored in such a medium.

In storing information by such process, it is necessary modulate theparticular form of radiation to be used r storing so as to have thecapacity to differentially or lectively irradiate a surface of a storagemedium. Modation can be effected by any conventional means whereby tmecharacteristic of radiation to be used for storage of formation isvaried in such a manner or to such a degree .at the resultingdiiferential radiation is capable of proicing photon-masking in thestorage medium.

During a storing or recording operation, the irradiating ith adifferential radiation pattern of a surface of a orage medium results inchemically and internally selecvely altering the initial composition ofsuch medium adcent at least one surface thereof. Such alteration results1 the creation of a masking layer which is capable of fferentiallycontrolling the passage of photon energy lerethrough in a mannerrepresentative of the initial pat- :rn of differential irradiation.

The masking layer, which, while within a storage meium is adjacent onesurface thereof, is in the nature of 1 image-wise recording of the inputinformation with him the diiferential radiation is modulated. The inputiformation recorded in the masking layer can be con- .dered to compriseor to be in the form of a plurality of iscrete resolution elements, eachresolution element being onsidered to be the smallest piece or bit ofinformation resent. In amplitude each such bit is the smallest detectalesignal level in a specified area of a recording medium, mi in size it isthe wave length of the highest spacial freuency within a specified areaof a recording medium.

In general, retrieval is accomplished using uniform elecron excitationof the previously irradiated storage meium. Thus, after storage anddevelopment (if necessary r desirable), a storage medium is placed in avacuum hamber and one surface thereof is exposed to a field of xcitedelectrons (e.g. an electron beam such as one genrated by an electrongun).

When the resulting medium with its stored information i subsequentlyscanned with an unmodulated electron eam, the fluorescent material isexcited sufliciently to mit photon energy material. As this photonenergy passes hrough the photon masking layer, there results a differncein photon energy emission along the scan route beween the differentiallyphoton masked and unmasked reas. This difference in photon energyemission is detected hotoelectronically. Photon energy detectors arewell ;nown and include such devices as photocells, photomul ipliers, andthe like.

Naturally, as in any storage and retrieval system in- 'olving a scanningoperation, the resolution efficiency of etrieval when practicing theprocesses of this invention lepends upon the relationship betweenunmodulated scanring beam size and the respective resolution elementscomirising the stored input information in the masking layer )f therecording medium. In order not to lose or fail to etrieve recordedinformation on readout, the relationship )etween the unmdoulatedscanning electron beam and each 'esolution element within a specifiedarea of a storage nedium surface should be such that the electron beamwidth measured in terms of the direction of relative veocity between thestorage medium and the beam is not greater than the width of individualresolution elements be read out (retrieved) measured in the samedirection.

While the scanning electron beam used to excite the iuorescent materialduring retrieval is referred to as being unmodulated, those skilled inthe art will appreciate that during the tracing of a raster by the beamin a scan field some sort of blanking may be employed during beam returnfor a new scan path in a raster pattern, for example one involvinghorizontal and vertical deflection, so that in this sense the beam istruly unmodulated only during its passage across a scan field.Furthermore, in certain situations, it may be desirable to impose uponthe unmodulated portion of such beam pulsed signal information or thelike, for example to cause particular effects upon, in, or about therecording or storage medium during readout. However, for retrievalpurposes differential photon emission from the masking surface of thestorage medium is achieved by an electron beam which is essentiallyuniform during residence time upon a storage medium. It will beappreciated that, as a consequence, the differential fluorescent patternproduced from the surface of such storage medium as a result of suchuniform beam impact produces photon emission bearing information whichneed not be at all associated with or carried by the unmodulatedscanning readout beam itself.

Apparatus description Referring to the drawings, it will be seen that inthe embodiment shown in FIGURES 1-3, the entire apparatus is enclosed inan envelope 9 which is adapted for evacuation and defines therewithin agenerally elongated, generally cylindrically shaped cavity. As thoseskilled in the art will appreciate, and as will become more apparentfrom the subsequent description herein, this envelope need only enclosethe portion of the apparatus which is to be traversed by the electronbeam.

In FIGURE 1 there is seen an electron source, herein designated in itseentirety by the numeral 10, Source 10 is adapted to emit along axis 11within envelope 9 a beam of electrons 12 depicted in outline form. Theelectron source 10 is seen to comprise a filament or cathode 13, a grid14 and an anode 15. The construction of electron sources is well knownto those of ordinary skill in the art.

An electron beam optical system herein designated in its entirety by themuneral 17 is positioned generally in the middle portion of envelope 9.This system 17 is adapted to focus the beam 12. In the embodiment shown,the system employs one electromagnetic lens 18 which is axially alignedwith the axis of beam 12 and one plate 19. Plate 19 has generallycircular, centrally located aperture 21 therein which serves to limitand collimate beam 12.

The construction of electron optical systems or means is likewise wellknown to those of ordinary skill in the art. It will be appreciated thatelectrostatic as well as electromagnetic lenses can be used. One canemploy more than one lens and a plurality of aperture plates forfocusing and collirnating an electron beam. Depending upon thecross-sectional size, shape, intensity, etc, of the beam needed, as wellas the type of electron source used and the type of recording mediuminvolved, those skilled in the art will appreciate that it is convenientto use any suitable combination of electron source and electron opticalsystem.

Positioned in envelope 9, in axial alignment with beam 12 after orfollowing that portion of the electron optical means or source 17 whichis furthest removed from the electron source 10, a beam deflection meansis provided. As shown in FIGURES 1 and 2, such beam deflection means isprovided by an electromagnetic deflection yoke 20, which is positionedadjacent the lens 18. The yoke 20 is of conventional construction and,like any beam deflection means, is adapted to cause the beam 12 to moveover predetermined portions of a scan field upon the face of platform24in a raster pattern (not shown). Platform 24 is located within theenvelope 9 in proximity to the end thereof opposite that in which theelectron source 10 is positioned. Lens 18 is chosen so as to have asuitably long focal length in order to maintain a considerable distancebetween lens 18 and platform 24 and thereby accommodate yoke 20 andreflector 27.

It will be appreciated that embodiments can be constructed which do notemploy beam deflection means. In these instances a relative velocitybetween the electron beam and the recorded information (i.e., therecording medium) can be provided by continuously moving the recordedinformation past (i.e., through) a stationary electron beam by some sortof conventional transport mechanism (not illustrated).

In order to position a prerecorded differentially photonemissive,electron beam-sensitive recording medium 23 within the scan field uponthe face of platform 24, some sort of positioning and/or supportingmeans is provided. As shown in FIGURES 1 and 2 such means comprises theplatform 24 over which is passed discontinuously, or continuously, aphoton-emissive, electron beam sensitive recording medium 23 which inthis case is in tape or strip form. Movement of the medium 23 acrossplatform 24 in front of beam 12 is provided by a conventional tapetransport mechanism, herein designated in its entirety by the numeral26. In some embodiments, the supporting means 24 and the mechanism 26can be combined. While in the embodiment shown, the tape transportmechanism 26, the platform 24, and the medium 23, are positioned withinthe envelope 9, those skilled in the art will appreciate thatalternative and equivalent arrangements can be conveniently used.

Positioned in envelope 9 between the yoke 20 and the platform 24 isaphoton reflective means, here a circular reflector 27. This reflector 27includes a spherically concave reflective surface 28 adapted to collectphoton emission within a large solid angle approaching a maximum ofabout 21r steradians measured with respect to the surface of a flatmedium 23 and the impinging beam 12. Naturally, if the surface of themedium is not flat, the available solid angle (the angle subtended bythe medium) can be greater than 21r and the reflective surface can bedesigned to collect over a greater solidangle than 211-. This reflector27 can be constructed of any conventional material, such as aluminum,silver, or the like, which is relatively stable and non-volatile underthe vacuum conditions conventionally associated with electron beamoperation. I found that aluminum is a particularly useful material forconstructing reflectors 27; I polish its reflective surface to such adegree that it becomes an effective reflector of photon energy. Ingeneral, I prefer to use concave reflective surfaces 28 which areellipticallyshaped, because the known optical properties associated withreflectors of such shape make it easier and preferable to concentrateand reflect from surface 28 towards a focal plane the photon emissionreceived from a medium 23.

In order to permit the beam 12 to pass unimpeded to the scan field 22through the reflector 27, reflector 27 is provided with a small aperture32 whose location and dimensions are so chosen as to permit the beam tomove over the entire scan field in a raster pattern without striking thereflector 27. In FIGURES 1 and 2, the

reflector 27 and aperture 32 are constructed so that the axis 11 of beam12 passes through the apex region of reflector 27. In general, thereflector 27 is positioned in envelope 9 after the electron opticalsystem 17 (and yoke 20, if used) and before the supporting means 24.Those skilled in the art will appreciate that a number of differentpossible constructions can be used for the reflective means in place ofthe reflector 27; a few alternative constructions are hereinafterdescribed. Also, such people will appreciate that the axis of reflector27 can be angularly disposed with respect to the axis 11 of beam 12 aswhen it is desired to position the photoelectric device to one side ofthe medium 23. In general however, a reflective means is so positionedas not to impede or affect the path of the beam. Thus, the

reflective means is always so positioned or constructed as to bediscontinuous at the path of the beam. In the embodiment of FIGURES 1and 2, the aperture 32 provides .the discontinuity in reflector 27.Naturally, it is preferred to keep the aperture 32 as small in itsdimensions as conveniently possible in order to maximize the amount ofphoton emission which can be collected by the surface 28 of reflector27, and reflected to the photon detector means (i.e., a photomultiplier29). Similarly, which it is preferred to use reflective means capable ofreflecting photon energy to a focal plane or point, it will beappreciated that for many purposes the focal plane can be poorlydefined, if at all.

Positioned generally after the medium 23 with respect to the electronsource 10 is a photon-detection means. Any conventional photon electricdetection means can be used in the embodiments shown, including devicessuch as photocells, photo-multipliers, and the like. For example, asshown in FIGURES 1 and 2, such a means is a photo-multiplier 29 whichconverts photon energy input into an electrical signal outputrepresentative of the photon energy input. The photo-multiplier 29 ispositioned in envelope 9 with respect to the reflector 27 and the medium23 so as to be in a position to collect as much as possible (ideallyall) of the photon rays 31, reflected from the surface 28 of reflector27. The photomultiplier 29, as a practical matter, can be positionedexactly at the image or focal plane (if one is definable) of the photonrays 31 or it can be positioned before or after such focal plane.

While the photon detection means as shown in the embodiments herein ispositioned inside envelope 9, those skilled in the art will appreciatethat in other embodiments such means can be positioned outside of suchan envelope 9. Thus, a window or lens (not shown) can be positioned inthe end of envelope 9. Then, the photomultiplier 29 can be suitablypositioned in front of such window outside envelope 9 and there used tosense the photon emission from medium 23 as reflected from reflector 27at some point outside of the envelope 9. In general, the photondetection means is positioned after the supporting means with respect tothe direction of. beam movement and adapted continuously to sense photonenergy reflected from the reflective means.

Those skilled in the artwill appreciate that, while in the embodimentsshown in the drawings the medium 23 is positioned generally normally tobeam 12, there is nothing particularly critical in such an arrangementand indeed it is possible to position the medium 23 at an angle withrespect to the beam 12. Similarly, it may be desirable to position'thereflector 27 at such angle as to reflect photon emission from medium 23towards photon detection means not axially aligned with beam axis 11.The exact angular interrelationship between medium 23 (or platform 24),reflector 27, beam 12 (or source 10), and photon detection means (likephoto-multiplier 29) can obviously vary widely from one embodiment toanother, as will readily be appreciated by those of ordinary skill inthe art.

Concerning the relationship between the reflector 27 and thephoto-multiplier 29 in FIGURES 1 and 2, it will be appreciated that,while it is generally convenient and even desirable to keep thephoto-multiplier 29 behind and spaced at a short distance from the backof the medium 23, it is quite possible and convenient in somecircumstances, depending upon the particular apparatus involved, theshape of the reflector surface 28, the type of photon sensitivedetection means employed, the type of medium 23 employed, and otherfactors, to position the photo-multiplier 29 at a level or position suchthat the photo-multiplier 29 is approximately equivalent to or inlateral alignment with the surface of the recording medium 23. Thephotomultiplier 29 is not positioned before or in front of the medium 23because in such an arrangement the photo-multiplier 29 would interferewith the oton emission from the medium 23 and to this extent t down uponthe light collection efliciency of any arngement involving reflector 27,medium 23, and photolltiplier 29. I

It will be appreciated that the apparatus of this inven- In isparticularly useful when one is reading out inrmation stored inphoton-emissive, electron beam-sensie media which are substantiallyopaque to the emitted totons since the radiation from such mediagenerally nstitutes a point source, in radiation distribution caus onlythe Zrr steradians on the electron beam struck to to be available forthe detection solid angle when the edia is flat at the position of beamimpact. Indeed, in der to assure that no transmission of electron energyphoton energy through a medium will occur, it is deable in manyinstances to position an opaque platform l back of the medium 23 as hasbeen done in the em- )diment shown in FIGURES 1-3 so as to assure no lsereadouts or collections of photon emission.

In the embodiment shown in FIGURES 1-3, together e yoke 20 and thetransport mechanism 26 comprise eans for relatively moving beam 12 overpredetermined )rtions of the differentially photon-emissive surface ofedium 23. While the embodiment employs a medium 23 tape form, it will beappreciated that the apparatus of is invention can also be used withmedia in sheet form.

'hen using sheet-like media, an appropriate conventional ieet or cardadvancement mechanism (not shown) can employed in place of transportmechanism 26. Of xurse, one can manually place a medium 23 on plattrm 24and not use either a tape transport mechanism a card advancementmechanism. However, apparatus 1' this invention requires some means forrelatively movg beam 12 over medium 23, so that if no such mecha- .sm isemployed then it is usually convenient to employ yoke 20 or equivalentbeam deflection means.

Also in the embodiment shown in FIGURES l-3, to- :ther the source 10 andthe electron optical system 17 )rnprise electron beam producing means.Such means eeds to be capable of producing an electron beam 12 aving awidth measured in the direction of relative alocity between beam 12 andmedium 23 which is not :eater than the width of individual resolutionelements not shown) associated with said medium 23 measured 1 the samedirection.

Photomultiplier 29 is positioned to receive photon enrgy reflected fromreflector means 27. The photomultilier 29 is adapted to continuouslysense the differential nd photon energy emitted by the medium 23 toproduce it electric signal output generally corresponding to thererecorded input information on medium 23. The photomlti-plier 29 sensesphoton energy reflected from reflec- )I' 27 at a rate not less than thatat which differences in hoton emission from the beam-struck surface ofmedium 3 occur during relative movement of beam 12 to medim 23. Suchdifferences in photon emission correspond individual resolution elementsin the recorded informaion, as indicated above.

Alternative embodiments In FIGURES 410 are shown alternative embodiments|f apparatus of this invention or portions thereof. Unless lth6I'WlS6indicated, the elements in each of these respecive figures are numberedthe same as those in FIGURES .-3 except that prime marks are addedthereto for disinguishing purposes.

In FIGURE 4, there is seen an alternative embodiment vherein thedeflection yoke and the reflector are one com- )osite structure hereindesignated in its entirety by the iumeral 33. The reflector-yokestructure 33 has a con- :ave reflective surface 34 formed in its endportion remote from the source (not shown). Structure 33 is advantage-)usly compact.

FIGURE discloses a portion of another alternative embodiment wherein aphotocell 36 is positioned outside 1 vacuum enclosure 37. An electronbeam 38 is shown passing through a magnetic deflection yoke 39 andimpinging on a prerecorded medium 41. The consequent photon emission,shown as rays 42, is reflected by a reflector 43 (constructed similarlyto reflector 27-) through a photon transmissive window 44 of glass orthe like to photocell 36. Window 44 is mounted across an aperture 4-6 inenclosure 37 by means of a conventional O-ring seal 47 and threaded cap48 which together seal the photon transmissive window 44 to enclosure37. The entire conventional transport mechanism 49 is shown housedwithin enclosure 37.

In FIGURE 6 is shown a' further alternative embodi ment wherein anelectron beam 51 strikes a prerecorded medium 52 and produces photonemission as rays 53. Rays 53 leave medium 52 and strike, respectively,reflectors 54 and 56 at various angles, from which they are reflectedonto respectively, photomultipliers 57 and 58. The entire assembly ishoused within an enclosure 59'. Medium 52 is opaque and stationaryduring scanning by beam 51, which is deflected in a horizontal patternby yoke 61. This configuration of apparatus elements provides twoindividual detectable images and greater reliability of signal detectionfor high resolution readout of high density information storage, forexample. When image production from recorded information is desired,this arrangement is sometimes less desirable than others describedherein because of photon aberration and image astigmatism. If more thantwo separate detectable images are desired, additional reflectors may beincorporated into the arrangement, space and configuration, parameterspermitting.

In FIGURES 7 and 8 (FIGURE 8 is reduced 25% due to space limitations) isillustrated an alternative reflector construction and diagrammatically amanner of using same. Here, an electron beam 62 after passing through anaperture of reflector 68 impinges upon a prerecorded medium 63generating rays 64, 65, and 66, among others (not shown). These rays 64,65, and 66 strike the reflective surface 67 of reflector 68. Owing tothe shape of surface 67 (shown generally in FIGURE 7 as a diametrical,vertical section), rays 64 and 66 which em-it from medium 63 inrespective directions closely parallel to but in an opposite directionfrom, beam 62, strike surface 67 and are directed laterally, radiallyand outwardly from the reflector axis (which in FIGURE 7 is coincidentwith beam axis 62). After next striking surface 67, the rays 64 and 66are reflected outwardly to photomultiplier 69 in the direction of beam62 movement. Ray which leaves medium 63 at an acute angle is reflecteddiametrically across surface 67 after impact thereagainst, to be finallyreflected outwardly to photomultiplier 69. The surface 67 of reflector68 is so shaped as not only to have the usual properties of anelliptical reflector but also to have the capacity to collect raysemitted substantially along or towards the axis of beam 62, which rayswould other wise represent lost energ since they would otherwise reflectback towards medium 63 after reflection from mirror having aconventional elliptically reflective surface. Naturally, the shape ofthe surface 67 of reflector 68 must be carefully formed for optimumresults.

In FIGURES 9 and 10 is shown one additional reflector constructionsuitable for use in apparatus of this invention. Here the reflectorcomprises a pair of spherical segments 70 and 71, respectively, eachpositioned with respect to one another and to the axis 72 of a beam 73approximately as suggested in FIGURES 9 and 10. FIG-' URE 9 can beconsidered to be a vertical, sectional View taken along the line 9-9 ofFIGURE 10.

In all embodiments, the photoelectric detection means is so positionedas to have reflected photon energy strike its photo-sensitive portions.

Having described my invention, I claim:

1. Apparatus for serial readout of a recording medium having adifferentially photon-emissive, electron beamsensitive surface, thedifferential photon emission from such surface being representative ofprerecorded input information, said apparatus comprising:

(a) a supporting envelope adapted for evacuation defining therewithin agenerally elongated cavity,

(b) electron beam producing means positioned in said envelope andadapted to emit generally lengthwise within said envelope atsubstantially uniform electron beam,

(c) means for supporting a differentially photon-emissive, electronbeam-sensitive recording medium in the path of said electron beam, thedifferentially photon emissive areas associated with a said recordingmedium being resolvable into a plurality of discrete resolutionelements,

(d) means for relatively moving said electron beam over predeterminedportions of a said recording medium when a said medium is so supported,

(c) said electron beam having during such relative movement a maximumwidth measured in the direction of relative velocity between saidelectron beam and a said recording medium not greater than the Width ofindividual resolution elements to be read out associated with a saidmedium measured in the same direction,

(f) photon reflective means positioned in said envelope between saidelectron beam producing means and said supporting means, said photonreflective means being discontinuous across the path of said beam,

(g) said reflective means including a concave reflective surface adaptedboth to collect photon energy emitted from the beam-struck surface ofsuch a recording medium Within a solid angle not larger than that solidangle subtended by said recording medium at the impact situs of saidbeam on such beam-struck surface and to reflect such energy in adirection generally away from said electron source, and

(h) photoelectric detection means positioned to receive photon energyreflected from said reflective means and adapted to continuously sensethe differential in said photon energy emitted and produce an electricsignal output generally representative of said prerecorded inputinformation on a said medium.

2. Apparatus for serial readout of a recording medium having adifferentially photon-emissive, electron beamsensitive surface, thedifferential photon emission from such surface being representative ofprerecorded input information, said apparatus comprising:

(a) a supporting envelope adapted for evacuation defining therewithin agenerally elongated, generally cylindrically-shaped cavity,

(b) an electron source positioned in one end of said envelope andadapted to emit generally axially within said envelope a substantiallyuniform beam of electrons, said source including a filament, a grid, andan anode,

(c) electron optical means positioned generally in the middle portion ofsaid envelope and adapted to focus said beam in a scan field definedacross said beam axis within said envelope in proximity to the oppositeend thereof,

(d) beam deflection means positioned in said envelope in axial alignmentwith said beam following that portion of said electron optical meansfurthest removed from said electron source and adapted to cause saidbeam to move over predetermined portions of said scan field in a rasterpattern,

(e) means for supporting a differentially photon-emissive, electronbeam-sensitive recording medium in the path of said electron beam, thedifferentially photon emissive areas associated with a said recordingmedium being resolvable into a plurality of discrete resolutionelements,

(f) means for relatively moving said electron beam over predeterminedportions of a said recording medium when a said medium is so supported,

(g) said electron beam having during such relative movement a maximumwidth measured in the direction of relative velocity between saidelectron beam and a said recording medium not greater than the width ofindividual resolution elements to be read out associated with a saidmedium measured in the same direction.

(h) photon reflective means positioned in said envelope between saidelectron beam producing means and said supporting means, said photonreflective means being discontinuous across the path of said beam,

(i) said reflective means including a concave reflective surface adaptedboth to collect photon energy emitted from the beam-struck surface ofsuch a recording medium within a solid angle approaching that solidangle subtended by said recording medium at the impact situs of saidbeam on such beam-struck surface and to reflect such energy in adirection generally away from said electron source, and

(j) photoelectric detection means positioned to receive photon energyreflected from said reflective means and adapted to continuously sensethe differential in said photon energy emitted and produce an electricsignal output generally representative of said prerecorded inutinformation on a said medium.

3. Apparatus for serial readout of a recording medium having adifferentially photon-emissive, electron beamsensitive surface, thediflerential photon emission from such surface being representative ofprerecorded input information, said apparatus comprising:

(a) a supporting envelope adapted for evacuation defining therewithin agenerally elongated, generally cylindrically-shaped cavity,

(b) an electron source positioned in one end of said envelope andadapted to emit generally axially within said envelope at substantiallyuniform beam of electrons, said source including a filament, a grid, andan anode,

(c) electron optical means positioned generally in the middle portion ofsaid envelope and adapted to focus said beam in a scan field definedacross said beam axis within said envelope in proximity to the oppositeend thereof,

(d) beam deflection means positioned in said envelope in axial alignmentwith said beam following that portion of said electron optical meansfurthest removed from said electron source and adapted to cause saidbeam to move over predetermined portions of said scan field in a rasterpattern,

(e) means for supporting a differentially photon-emissive, electronbeam-sensitive recording medium in said envelope in the path of saidelectron beam, the differentially photon emissive areas associated witha said recording medium being resolvable into a plurality of discreteresolution elements,

(f) means for relatively moving said electron beam over predeterminedportions of a said recording medium when a said medium is so supported,

(g) said electron beam having during such relative movement a maximumwidth measured in the direction of relative velocity between saidelectron beam and a said recording medium not greater than the width ofindividual resolution elements to be read out associated with a saidmedium measured in the same direction.

(h) said envelope having defined in its opposite end portion a photontransmissive window,

'(i) photon reflective means positioned in said envelope between saidelectron beam producing means and said supporting means, said photonreflective means being discontinuous across the path of said beam, (j)said reflective means including a concave reflective surface adaptedboth to collect photon energy emitted from the beam-struck surface ofsuch a recording 1 1 2 medium within a solid angle approaching a 211-steradians over the impact situs of said beam on such beam-strucksurface and to reflect such energy in a direction generally away fromsaid electron source,

(b) means for collecting photon energy emitted from the so beam-strucksurface of said medium Within a and 5 solid angle not larger than thatsolid angle subtended (k) photoelectric detection means positionedoutside by said medium at the impact situs of said beam on of saidenvelope adjacent said window so as to resuch beam-struck surface andfor reflecting such ceive photon energy reflected from said reflectiveenergy in a direction generally away from said elecmeans and adapted tocontinuously sense the differtron source, and

ential in said photon energy emitted and produce an (c) means forsensing photon energy from said means electric signal output generallyrepresentative of said prerecorded input information on a said medium.

for collecting and reflecting and for converting such energy into acorresponding electric signal output,

thereby to electronically retrieve prerecorded information from saidmedium.

4. Apparatus for electronically retrieving prerecorded formation from arecording medium having a difieren- ,lly photon-emissive, electron beamresponsive surface, e differential photon emission from such surfacebeing presentative of prerecorded input information, said apratuscomprising in combination:

References Cited UNITED STATES PATENTS (a) means for generating and forrelatively moving 4/1956 Rajchman et 340173 a substantially uniformelectron beam over predeter- 2999163 9/1961 Beese 313 92 X minedportions of a said recording medium, said elec- 3099762 7/1963 Hertz313*275 X tron beam having during such relative movement 3,181,1724/1965 Boblett thereof a maximum Width measured in the direction ofrelative velocity between said electron beam and BERNARD KONICK P'lmaryExammer' said medium not greater than the width of individual J.BREIMAYER, Assistant Examiner.

3. APPARATUS FOR SERIAL READOUT OF A RECORDING MEDIUM HAVING ADIFFERENTIALLY PHOTON-EMISSIVE, ELECTRON BEAMSENSITIVE SURFACE, THEDIFFERENTIAL PHOTON EMISSION FROM SUCH SURFACE BEING REPRESENTATIVE OFPRERECORDED INPUT INFORMATION, SAID APPARATUS COMPRISING: (A) ASUPPORTING ENVELOPE ADAPTED FOR EVACUATION DEFINING THEREWITHIN AGENERALLY ELONGATED, GENERALLY CYLINDRICALLY-SHAPED CAVITY, (B) ANELECTRON SOURCE POSITIONED IN ONE END OF SAID ENVELOPE AND ADAPTED TOEMIT GENERALLY AXIALLY WITHIN SAID ENVELOPE A SUBSTANTIALLY UNIFORM BEAMOF ELECTRONS, SAID SOURCE INCLUDING A FILAMENT, A GRID, AND AN ANODE,(C) ELECTRON OPTICAL MEANS POSITIONED GENERALLY IN THE MIDDLE PORTION OFSAID ENVELOPE AND ADAPTED TO FOCUS SAID BEAM IN A SCAN FIELD DEFINEDACROSS SAID BEAM AXIS WITHIN SAID ENVELOPE IN PROXIMITY TO THE OPPOSITEEND THEREOF, (D) BEAM DEFLECTION MEANS POSITIONED IN SAID ENVELOPE INAXIAL ALIGNMENT WITH SAID BEAM FOLLOWING THAT PORTION OF SAID ELECTRONOPTICAL MEANS FURTHEST REMOVED FROM SAID ELECTRON SOURCE AND ADAPTED TOCAUSE SAID BEAM TO MOVE OVER PREDETERMINED PORTIONS OF SAID SCAN FIELDIN A RASTER PATTERN, (E) MEANS FOR SUPPORTING A DIFFERENTIALLYPHOTON-EMISSIVE, ELECTRON BEAM-SENSITIVE RECORDING MEDIUM IN SAIDENVELOPE IN THE PATH OF SAID ELECTRON BEAM, THE DIFFERENTIALLY PHOTONEMISSIVE AREAS ASSOCIATED WITH A SAID RECORDING MEDIUM BEING RESOLVABLEINTO A PLURALITY OF DISCRETE RESOLUTION ELEMENTS, (F) MEANS FORRELATIVELY MOVING SAID ELECTRON BEAM OVER PREDETERMINED PORTIONS OF ASAID RECORDING MEDIUM WHEN A SAID MEDIUM IS SO SUPPORTED, (G) SAIDELECTRON BEAM HAVING DURING SUCH RELATIVE MOVEMENT A MAXIUM WIDTHMEASURED IN THE DIRECTION OF RELATIVE VELOCITY BETWEEN SAID ELECTRONBEAM AND A SAID RECORDING MEDIUM NOT GREATER THAN THE WIDTH OFINDIVIDUAL RESOLUTION ELEMENTS TO BE READ OUT ASSOCIATED WITH A SAIDMEDIUM MEASURED IN THE SAME DIRECTION. (H) SAID ENVELOPE HAVING DEFINEDIN ITS OPPOSITE END PORTION A PHOTON TRANSMISSIVE WINDOW, (I) PHOTONREFLECTIVE MEANS POSITIONED IN SAID ENVELOPE BETWEEN SAID ELECTRON BEAMPRODUCING MEANS AND SAID SUPPORTING MEANS, SAID PHOTON REFLECTIVE MEANSBEING DISCONTINUOUS ACROSS THE PATH OF SAID BEAM, (J) SAID REFLECTIVEMEANS INCLUDING A CONCAVE REFLECTIVE SURFACE ADAPTED BOTH TO COLLECTPHOTON ENERGY EMITTED FROM THE BEAM-STRUCK SURFACE OF SUCH A RECORDINGMEDIUM WITHIN A SOLID ANGLE APPROACHING A 2$ STERADIANS OVER THE IMPACTSITUS OF SAID BEAM ON SUCH BEAM-STRUCK SURFACE AND TO REFLECT SUCHENERGY IN A DIRECTION GENERALLY AWAY FROM SAID ELECTRON SOURCE, AND (K)PHOTOELECTRIC DETECTION MEANS POSITIONED OUTSIDE OF SAID ENVELOPEADJACENT SAID WINDOW SO AS TO RECEIVE PHOTON ENERGY REFLECTED FROM SAIDREFLECTIVE MEANS AND ADAPTED TO CONTINUOUSLY SENSE THE DIFFERENTIAL INSAID PHOTON ENERGY EMITTED AND PRODUCE AN ELECTRIC SIGNAL OUTPUTGENERALLY REPRESENTATIVE OF SAID PRERECORDED INPUT INFORMATION ON A SAIDMEDIUM.